Mosquitoes represent a wide number of insects belonging to the order Diptera, suborder Nematocera, family Culicidae. There are approximately 3500 species of mosquitoes grouped into 41 genera.
Vector-borne diseases transmitted by mosquitoes (malaria, filariasis, dengue, chikungunya, yellow fever, Zika virus and other arboviruses) are the major public health concerns in tropical and sub-tropical areas of the world. Poor and ineffective drainage systems in urban areas, especially during rainy seasons, and irrigation ditches in farmland provide several mosquito breeding places.
Among the mosquito populations, Anopheles stephensi and An. gambiae are the main malaria vectors in Asia and Africa, respectively; whereas Aedes aegypti and Ae. albopictus are the main vectors of arboviruses.
All these vector-borne diseases afflict mainly poor countries where more than two billion people live in endemic regions.
The common approaches to fight vector-borne diseases rely on the use of chemical insecticides or synthetic larvicides targeting adults and larvae. However, the development of mosquitoes showing insecticide-resistance to different classes of synthetic compounds, such as pyrethroids, organophosphates, organochlorides and carbamates, has determined the research of new and “safe” formulations to control mosquito populations. Moreover, the toxicity of available chemical products on human beings and animals as well, their high operational costs and the subsequent environmental pollution, have caused the need for developing new approaches to control vector-borne diseases.
Mosquito Life Cycle
Mosquitoes go through four developmental stages in their life cycles: eggs, larvae, pupae and adult. The first three stages are aquatic and persist until about two weeks and depend on the mosquito species and the external environmental conditions. The female mosquito lifespan is around three weeks while for a male it's just two weeks. Adult females lay 50-200 eggs per oviposition. The eggs are quite small (about 0.5×0.2 mm). Eggs are laid singly and directly on water. Eggs are not resistant to drying and hatch within 2-3 days, although hatching may take up to 2-3 weeks in colder climates.
Larvae emerge from the eggs. The Anopheles larvae do not present a respiratory siphon, like other mosquitoes (e.g. the Culex and Aedes genera), so its body is parallel to the surface of the water. In contrast, feeding larvae of non-anopheline mosquito species attach itself to the water surface through its posterior siphon, with their body pointing downwards. The mosquito larvae have a well-developed head with mouth brushes used for feeding, a large thorax and a nine-segment abdomen. The larvae feed on zooplankton, algae, bacteria, and other microorganisms in the surface microlayer.
To lay their eggs female mosquitoes need to mate, to inseminate the eggs and one or more blood feeding to develop the eggs. Immediately after the oviposition, freshly oviposited eggs are soft and white. Since the eggshell in insects represents an important barrier that prevent the embryo from damages and infections, for this reason it undergoes through different processes of hardening and darkening that gives to it more resistance to external environment. In this sense, the amino acid tyrosine plays a crucial role in the egg chorion melanization. In the melanization pathway, tyrosine is converted in L-Dopa by tyrosine hydroxylase and L-Dopa is converted in dopamine by Dopa decarboxylase, different prophenol oxidase are then involved in the formation in both L-Dopa melanin from L-Dopa and Dopamine melanin from Dopamine.
Larvae develop through four stages, or instars, after which they develop into pupae. At the end of each instars, the larvae grow up, modifying their exoskeletons, to allow for further growth. First-stage larvae are about 1 mm in length; fourth-stage larvae are normally 5-8 mm in length.
The processes from egg-laying to adult inception depends on temperature and environmental conditions, with a minimum time of seven days.
The larvae can survive in a wide range of habitats and they have been found in freshwater or saltwater marshes, swamps, rice fields, the edges of streams and rivers, and small, temporary rain pools.
The pupae have the shape of a comma if it's seen from the side. The head and thorax are joined into a cephalothorax with the abdomen curving around underneath. As with the larvae, pupae must come to the surface frequently to breathe, through a pair of respiratory trumpets on their cephalothoraces. After a few days as a pupa, the dorsal surface of the cephalothorax is broken and the adult mosquito emerges. The pupal stage lasts around 2-3 days in temperate areas.
The duration from egg to adult can considerably vary depending on species, and it is strongly influenced by external environment. Mosquitoes can develop from egg to adult from 7 to 14 days according to environmental conditions.
Most existing insecticides available in the market are constituted by effective ingredients but are also characterized by specific toxicity degrees for human beings and animals, as well.
The elimination of mosquito larvae and pupae using a not-toxic formulation does not pollute aquatic environments substantially eliminating risk of intoxication for both animals and human beings.
Existing references known to kill mosquitoes include U.S. Pat. Nos. 5,196,200, 5,205,065, 5,228,233, 5,281,621, 5,327,675, 5,417,009, 5,464,626, 5,521,165, 5,633,236, 5,665,781, 5,698,210, 5,716,602, 5,855,903, 6,077,521, 6,267,953, 6,306,415, 6,562,841, 6,593,299, 6,605,643, 6,800,294, 6,809,078, 6,825,006, 7,198,797, 7,378,557, 8,454,983, 8,696,987, 8,900,553, 9,549,898, US20070154504, US20080193387, US20080213198, US20090018192, US20100233146, US20100310685, US20110229543, US20130296370, US20160360758, US20170215432 and WO2016018937.
It is an object of the invention to improve upon the deficiencies in the prior art.